Spinnerets



March 14, 1967 D. SHICHMAN SPINNERETS Filed July 22, 1965 I N VEN TOR 0AlV/EZ JH/CH/VA/V ATTORNEY United States Patent M 3,308,504 SPINNERETSDaniel Shichman, Cedar Grove, N.J., assignor to United States RubberCompany, New York, N.Y., a corporation of New Jersey Filed July 22,1965, Ser. No. 473,920 14 Claims. (Cl. 18-8) This invention relates tothe art of manufacturing spinnerets employed in the production ofartificial or synthetic filaments or fibers by extrusion processes, andparticularly concerns the formation of extrusion orifices or holes ofvarious desired cross-sections in such spinnerets.

The formation of extrusion openings or orifices of special or oddshapes, i.e. of non-circular cross-sections, in spinnerets or jet cupsfor synthetic filament-spinning apparatus generally entails punchingand/or drilling the desired hole shapes in the metal cups or plates.Other techniques which may be employed are spark and chemical erosion ofthe metal, and even the use of electron beams and lasers has beenattempted. See, for example, an article entitled Spinneret Makers EnjoyFibers Surge, in Chemical & Engineering News, February 1, 1965, pages 34to 36. Such fabricating methods are, however, relatively expensive, andespecially so if they fail to provide the edge sharpness and smoothnessof surface finish required. Moreover, with these methods it is bothdifficult and expensive to achieve a high capillary ratio, i.e. theratio of the length to the diameter of the orifice. In this context, thediameter of the orifice is the diameter of a circle which would have thesame area as the noncircular opening.

It is an object of the present invention, therefore, to provide noveland improved methods for fabricating spinnerets and for forming jetopenings or extrusion orifices therein.

Another object of the present invention is the provision of spinneretshaving extrusion orifices of various crosssectional shapes formedtherein.

Still another object of the present invention is the provision of suchspinnerets and of methods of making the same which are characterized bythe attainment of smooth surface finish and high capillary ratios in thefinished orifices with a minimum of expense and technical diffioulty.

The foregoing and other objects, characteristics and and advantages ofthe present invention will be more fully understood from the followingdetailed description thereof when read in conjunction with theaccompanying drawings, in which:

FIGS. 1, 2 and 3 are graphic representations, greatly enlarged, of threetypes of odd cross-section spinning or extrusion orifices and illustratethe manner of construction and dimensioning thereof in accordance withthe present invention;

FIG. 4 is a fragmentary bottom plan view of a spinneret provided with aplurality of jet openings or extrusion orifices having the shapeillustrated in FIG. 1;

FIG. 5 is a fragmentary, exploded perspective bottom view of such aspinneret and illustrates the method of achieving the desired orificecross-section;

FIG. 6 is a sectional view taken along the line 6-6 in FIG. 4;

FIG. 7 is a fragmentary bottom plan view, similar to FIG. 4, of aspinneret provided with a plurality of jet openings or extrusionorifices having the shape illustrated in FIG. 2;

FIGS. 8 and 8a are graphic representations of modified forms of theorifice shape illustrated in FIG. 2;

FIGS. 9 and 9a are perspective elevational views of respective elementsemployed in imparting to an extrusion orifice the cross-sectional shapesillustrated in FIGS. 8 and 8a; and

3,308,504 Patented Mar. 14, 1967 FIGS. 10 and 11 are graphicrepresentations of still other types of odd cross-section spinningorifices which can be designed in accordance with the principles of thepresent invention.

Generally speaking, in the production of synthetic filaments, afilament-forming material in liquid phase, e.g. either a solution in avolatile solvent or a melt, is spun by extrusion under high pressurethrough the jet open ings or orifices of spinnerets into chambers orcabinets where the streams solidify. Such a cabinet may contain, asrequired, either an evaporative atmosphere such as heated air, or aliquid bath. Both dry and melt spinning systems equipped with suchspinnerets for converting suitable raw materials into filaments, yarn ortow are well known and need not be illustrated or described in detailherein.

It is also Well known that the jet openings or orifices of spinneretsmay be circular, polygonal or otherwise cross-sectionally shaped, andthat extrusion of the filament-forming material, i.e. the dope or themelt, through any such opening results in the formation of a filamenthaving a cross-sectional shape determined in part by the shape of theopening and to a certain extent also by such factors as the nature ofthe material, the manner and rate of solidification of the filament, andthe drawdown ratio (ratio of take-up speed to extrusion speed). Bul bousor circular cross-section filaments formed by spinning through circularorifices are the most common, of course, but for many applications, bothof a textile and non-textile nature, special non-bulbous cross-sectionfilaments are found highly desirable and advantageous by virtue of theirgreater surface area per filament denier, bulk, compressibility, beamstrength and elasticity, and their enhanced receptiveness to dyeing andresistance to abrasion and soiling.

The present invention is principally concerned with (albeit not limitedto) the manufacture of spinnerets having formed therein one or more-jetopenings or extrusion orifices the cross-sectional shape of which is nota circle but instead is a polygon at least one of the sides of which isessentially either fiat or convex or concave viewed inwardly of theperiphery of the orifice.

Thus, in accordance with one aspect of the present invention, there isprovided a novel spinneret having one or more jet openings each of whichis shaped substantially in the form of a triangle having inwardly convexcurved sides defined by three arcuate side walls which lie alongrespective parts of the circumferences of three circles each contiguous,e.g. tangent, to the other two. In accordance with other aspects of thepresent invention, each such jet opening may have the shape of a polygonwith four or more inwardly convex curved sides defined by a number ofarcuate side walls which lie along respective parts of thecircumferences of a corresponding number of circles each contiguous,e.g. tangent, to two of the other circles. In accordance with stillother aspects of the present invention, the surface of each side walldefining such an orifice may be provided with longitudinal depressionsor projections extending along the entire length of the orifice, and asdesired one or more sides of each orifice may be convex while others areconcave inwardly of the orifice or fiat.

Referring now first to FIGS. 1 and 4-6 of the drawing, the spinneret 19(which is generally in the form of a circular plate or similarstructure) is shown as being pro vided, in accordance with oneembodiment of the present invention, with a plurality of cusped jetopenings or orifices 11 each of which is shaped substantially in theform of a triangle having inwardly curved sides 12, 13 and 14. Asclearly shown in FIG. 1, the sides 12, 13 and 14 of each opening 11constitute arcs of three circles 15, 16 and 17 which are tangent to eachother at the points 18, 19 and 20. The spinneret may be provided with asfew as one and as many as several hundred such orifices, and these maybe arranged and distributed throughout the expanse of the spinneret inany desired manner, for example in one or more concentric circles or inrespective parallel rows and tiers, or otherwise. Each such orifice mayhave a diameter (as that term has been defined herein) between about.004 and .040 inch and preferablyv between about .010 and about .020inch, and it will become clear as the description proceeds that thelength of each orifice may be such as to provide a capillary ratio oflength to diameter both as slow as 1:1 and as high as 20:1 or more.

The spinner-ct 10 (see FIGS. 5 and 6) generally comprises a plate member10a of substantial diameter and thickness, and the formation of theorifices 11, in accordance with the present invention, is as follows.Initially, a plurality of relatively wide bores 21 is drilled into theplate 10a from the top surface 1% of the latter, each such bore beinglocated substantially in coaxial relationship with the intended locationof the respective one of the desired orifices 11. The bores 21, whichmay have a diameter between. about .0625 and about .125 inch, areconventionally formed by drilling to a depth of between about /2 and /3of the thickness of the plate. At this point, a set of three circularbores 24, 25 and 26 is drilled into the plate 16a from the bottomsurface 100 thereof all the way to the innermost end of each bore 21along three centers located at the .apices of an equilateral triangleand so spaced from each other that the three circles are tangent to oneanother. The innermost ends of the sets of bores 24 and 26 thus haverespective, essentially prolate, segments of their circularcross-sections directly aligned with corresponding segments of thecircular cross-sections of the bores 21 (see FIG. 4).

As the last one of each set of the bores 24 to 26 to be drilled reachesthe level of the bottom of its associated bore 21, the respectiveconcavely triangular rod of metal which constitutes the remains of thematerial drilled out of the plate from the bottom thereof becomescompletely separated from the bulk of the plate and can be removed,leaving the composite opening shaped as shown in FIG. 5, the so-formedtrilobar bore terminating in the plane of the innermost end of the bore21 and the shoulder 21a surrounding the same.

Into the sets of bores 24, 25 and 26 there are then press-fittedrespective sets of pins 27, 28 and 29 of the same circular diameter asthe bores. The pins of each of these sets, being precisely circular incross-section and tangent to one another, will thus define between thema cusped, concavely triangular space constituting the respectiveextrusion orifice 11 of the spinneret. The actual lengths of the pins 27to 29 employed will, as previously explained, depend both on the size ofthe spinneret plate and on the desired capillary ratio to be attained.Merely by way of example, for an orifice 11 having a diameter of aboutmils, the lengths of the pins 27 to 29 and thus the axial length of theorifice 11 would be about 300 mils where a :1 capillary ratio isdesired. Moreover, the present invention makes it possible to increasethe capillary ratio of the orifice without increasing the thickness ofthe spinneret plate, a result which is achieved by using pinsappropriately longer than the bores 24 to 26, as indicated in FIG. 6. Itwill be understood, of course, that the cross-sectional size of each ofthe orifices 11 may be varied by appropriately increasing or decreasingthe diameters of the drilled circular bores 24 to 26 (and the diametersof the corresponding pins 27 to 29), ie the diameters of the circles 15,16 and 17 referred to in connection with FIG. 1.

The same principles of odd-shaped jet orifice formation are, inaccordance with other aspects of the present invention, applicable tothe making of spinnerets provided with one or more polygonal jetopenings the shapes of which differ from that so far described. Thus, aspinneret (see FIG. 7) may have extrusion orifices 30 each of which(FIG. 2) has the shape of a quadrilateral with four inwardly curvedsides 31, '32, 33 and 34 each of which constitutes an arc of .arespective one of four circles 35, 36, 37 and 38 tangent to one anotherat the points 39, 40, 41 and 42. It will be apparent that in theformation of each orifice 30, after the respective bores 21 have beendrilled into the spinner-ct plate from the top surface thereof, fourbores corresponding to the circles 35 to 38 are drilled into the platefrom the bottom face thereof at respective centers located at thecorners ofa square, so that each such bore is tangent to the twoadjacent bores. Again, at the completion of the drilling of the lastsuch bore, the concavely sided piece of solid material will becompletely separated and removable from the plate, whereupon the firminsertion of rigid pins 43 to 46 of precisely circular cross-sectioninto the respective bores will define therebetween the cusped orifices30 having four side walls defined by the respective surface portions ofthe pins corresponding to the solid-line arcs 31 to 34 shown in FIG. 2.As in the case of the orifice 11, of course, the size of the orifice 30can be varied by a suitable choice of the diameters of the circles 35 to38 and of the pins 43 to 46 inserted into the respective bores.

Similarly, a spinneret may be made with cusped orifices 47 (FIG. 3)having five concavely curved sides 48 to 52 constituted by respectivearcs of a plurality of circles 53 to 57 each of which is tangent to thetwo adjacent circles. The manner of formation of the orifice 47 isidentical with that heretofore described for the orifices 1'1 and 30, towit it is formed by initially drilling a bore corresponding to the bore21, then drilling five circular bores tangent to one another, asindicated by the circles 53 to 5-7, with their centers located at theapices of a regular pentagon, and finally press-fitting a set of rigidpins of the identical diameter into each of the so-formed bores, leavingtherebet-ween the orifice 47. It will be understood that these sametechniques can also be emplgyed for the formation of orifices havingmore than five si es.

In general, the cross-sectional shape of filaments spun by extrusionthrough such orifices as 11, 30, 47 etc. will depend among other thingsboth on the raw material employed and the attendant extrusionconditions, and a melt spun filament extruded through a given orificemay difier in shape from a dry spun filament extruded through the sameorifice. Inasmuch as such filaments and their shapes do not constitute apart of the present invention, however, they are neither illustrated nordescribed in detail herein.

It will further be understood that the cross-sectional shapes of anyorifice of the types herein described may be varied in other ways so asto admit of the formation of still different filament cross-sections. Arepresentative type of modification of cross-sectional shapeisillustrated in FIG. 8, where a four-sided orifice 30 is shown which isgenerally identical to the orifice 30- of FIG. 2 and differs therefromonly in that longitudinally extending grooves 58 to 61 are formed in theside walls of the orifice. The deformations or grooves 58 to 61 can beformed by milling or otherwise suitably cutting the necessary materialout of each of the pins 62 to be press-fitted into the respective boresdrilled into the bottom face of the spinneret plate, as indicated at 63in FIG. 9. Moreover, more than one such groove or slot may be providedin each side wall of the orifice, and either one or a plurality of thedesired deformations may be provided on less than all the walls of theorifice. Alternatively, in lieu of grooves, each pin 64 (FIG. may beprovided with one or more ribs or like projections 65 which in thefinished spinnere-t would. project from the walls of the orifice 30-"(*FIG. 8a) in-- wardly of the latter so as to alter its cross-sectionalshape; accordingly.

Some other types of modifications of cross-sectional shape areillustrated in FIGS. 10 and 11 where two three-.

sided orifices 1-1' and 11" are shown. Each of these orifices aregenerally the same as the orifice 11 of FIG. 1 and differs therefromonly in that the inwardly convex side 14 is replaced in one case by aside 14' which is concave inwardly of the orifice, and in the other caseby a side 14 which is plane and not curved. Clearly, the same could bedone with two or all of the sides of the orifice 11, and with any numberor all of the sides of the orifices 30, 47 and 30, by the appropriateshaping of the orifice wall-defining surface of each pin involved. Inany such variation, of course, wherever there is a juncture between anytwo sides which are not inwardly convex, the orifice is, strictlyspeaking, not cusped as that term is generally employed, but for thepurposes of this application the term cusped is to be interpreted tocover such junctures as well.

It will also be apparent that the principles of the present inventionextend to the formation of orifices by the drilling of circular bores ofunequal diameters and in such a way that they need not be tangent toeach other. Merely, by way of example, any one or more of the variouscircles representing such bores in FIGS. 1 to 3, 8, 10 and 11 couldintersect one or both of its two adjacent circles, and in fact for someorifice cross-sections the drilling of two intersecting bores willsufiice, assuming that the pins or inserts are suitably shaped at theirfacing surfaces to define the necessary space therebetween. Moreover,the polygonal cross-sections need not be regular and equilateral, thedimensions and shape of any orifice wall being determined solely by theamount of material removed from the pin defining that wall and by thepattern of such removal.

Still further, the principles of the present invention may also beapplied to the formation of circular and straightsided polygonal orificecross-sections. Merely to illustrate this aspect, a circular orificecould be formed by milling into each of the pins to be inserted into aset of bores in a spinneret, e.g. the pins 27 to 29 shown in FIG. 5,respective longitudinal concavities of circular cross-sectionalcurvature and having identical constant radii of curvature of suitablemagnitude, while a straight-sided triangle could be formed by millingrespective flats onto the pins.

The present invention thus provides a novel method of forming anextrusion orifice in a spinneret which method, in its broadestessentials, is characterized by the steps of (a) drilling a set of atleast two laterally contiguous bores in the spinneret plate and (b)refilling such bores with hard pins of appropriate peripheral surfacecontours so that there is a certain space defined between the pins whichconstitutes the orifice of the desired cross-sectional shape. The methodof the present invention is, consequently, seen to be possessed ofalmost infinite versatility in respect of the types and sizes of orificecross-sections attainable thereby, and also in respect of the attainablecapillary ratios. Moreover, it is further possessed of the technologicaladvantage of enabling an orifice of relatively small effective diameterto be formed through an initial formation of a plurality of considerablylarger diameter bores, as will be appreciated from the fact that threebores (15 to 17 in FIG. 1 or 24 to 26 in FIG. of .062" diameter make anorifice (11 in FIG. 1) of only .013" diameter.

As previously indicated, the number of jet openings or orifices in anygiven spinneret may be as high as several hundred, and thus the totaldenier of the filamentary material collected from each spinneret willdepend both on the number and sizes of the orifices. In accordance withthe present invention, it is also possible to provide in any givenspinneret a plurality of orifices of different cross-sections so as toprovide for the formation of a filament bundle composed of a mixture offilaments of correspondingly different cross-sections. Merely by way ofexample, a spinneret may contain any two or more of the types oforifices 11, 30, 47, 30' etc. of the present invention, or any one ormore of these types intermingled with one or more orifices of any othershape, such as circular orifices, crescent-shaped orifices, etc.

The orifice-defining metal pins are preferably hardened and, since theycan be extruded or machined within relatively close tolerances, makepossible the formation of orifices of precisely predetermined dimensionsand highly smooth interior surface finishes. Various techniques can alsobe used to prevent any leakage of the filament-forming material aroundthe pins. Merely by way of example, if hardened pins are inserted in arelatively softer metal spinneret plate, finish grinding of the lowersurface of the latter will cause the softer metal to flow over the pinswhere they adjoin the plate. This will have no adverse effect on thesharpness of the end edges of the capillary walls, however, since thehardened metal of which the pins are made will resist the tendency toflow under grinding. Alternatively, the pins may be silversoldered inplace to effect the required seal.

Spinnerets having orifices of the types herein set forth may be employedin spinning substantially all known filament-forming materials,including nylon, rayon, acetate, polyesters, acrylonitrile polymers andcopolymers, polymers and copolymers of olefins and vinyl esters such asethylene, propylene, vinyl chloride, vinylidene chloride, vinyl acetate,etc., ethyl cellullose, and the like.

In an actual test, a spinneret having formed therein 35 orifices of thetype shown in FIGS. 1 and 4 and each defined between arespective set ofthree hard-surfaced inch diameter steel pins press-fitted intocorresponding drilled holes and having a capillary length of 1 inch toyield a capillary ratio of better than 14:1, was employed in a meltspinning operation. The raw material was polypropylene furnished byHercules Powder Company. The extruder temperature was 540 F., theextruder pressure 3700 p.s.i., the spinning head temperature 510 F., thespinning rate 7 pounds per hour, and the drawdown ratio of 5.09. After acontinuous run of 51 hours and 50 minutes, approximately 360 pounds of aconvexly triangular cross-section filament yarn had been produced with adenier of 210 and a tenacity of 5.35 grams per denier. This yarn hadacceptable dyeability and is highly suited for use in the manufacture ofupholstery, carpeting, clothing and drapery fabrics.

It is to be understood that the foregoing disclosure is for purposes ofillustration only, and that the various structural and operationalfeatures, relationships and conditions set forth in detail herein aresubject to modification in a number of ways none of which involves adeparture from the spirit and scope of the present invention as definedin the hereto appended claims.

Having described my invention, What I claim and desire to secure byLetters Patent is:

1. A spinneret provided with at least one cusped extrusion orificehaving at least three side walls which are convex inwardly of theorifice, said orifice being defined between a set of pins of circularcross-section arranged in a ring formation with each pin tangent to twoof the other pins, and said walls of said orifice being constituted bythe minor arcs of the circumferential pin surfaces lying between theirpoints of tangency.

2. A spinneret having at least one extrusion passage way terminating inan orifice of odd cross-sectional shape, said passageway comprising afirst bore extending in from one face of the spinneret through apredetermined portion of the thickness thereof, and said orifice beingin communication with and extending from the inner end of said firstbore to the other face of said spinneret, said orifice being of cuspedcross-sectional shape and having at least three side walls which areconvex inwardly of the orifice, said orifice being defined between a setof pins of circular cross-section arranged in a ring-like formation witheach pin tangent to two of the other pins, and said Walls of saidorifice being constituted by the minor arcs of the circumferential pinsurfaces lying between their points of tangency.

3. A spinneret having at least one extrusion passageway terminating inan orifice of odd cross-sectional shape, comprising a plate providedwith a first circular bore drilled in from one face of said platethrough a predetermined portion of the thickness of said plate, and withat least three additional circular parallel bores, each tangent to twoof the other additional bores, drilled in from the other face of saidplate to the inner end of said first bore and on respective centerslocated at the corners of a polygon substantially enclosing thecross-section of said first bore, and a like number of hardened metalpins of the same diameter as said additional bores tightly fitted intothe latter, thereby to define a cusped orifice having inwardly convexwalls constituted by the minor arcs of the circumferential pin surfaceslying between their points of tangency.

4. A spinneret according to claim 3, wherein said pins are three innumber and are fitted into three of said additional bores centered atthe apices of a triangle, and said orifice has the cross-sectional shapeof a triangle with inwardly convex sides.

5. A spinneret according to claim 3, wherein said pins are four innumber and are fitted into four of said addi tional bores centered atthe corners of a quadrilateral, and said orifice has the cross-sectionalshape of a quadrilateral with inwardly convex sides.

6. A spinneret according to claim 3, wherein said pins are five innumber and are fitted into five of said additional bores centered at thecorners of a pentagon, and said orifice has the cross-sectional shape ofa pentagon with inwardly convex sides.

7. A spinneret according to claim 3, wherein there are provided aplurality of additional orifices at least some of which are identical tosaid first-named orifice.

8. A spinneret according to claim 3, wherein on the orificewall-constituting surface portions of at least some of said pins thereis provided at least one surface deformation changing the orificecross-section correspondingly.

9. A spinneret according to claim 8, wherein said deformation comprisesa surface depression.

10. A spinneret according to claim 8, wherein said deformation comprisesa surface protuberance.

11. A spinneret having at least one extrusion passageway terminating inan orifice of predetermined cross-sectional shape, comprising a plateprovided with a first circular bore drilled in from one face of saidplate through a predetermined portion of the thickness of said plate,and with at least three additional circular parallel bores, eachcontiguous to two of the other additional bores, drilled in from theother face of said plate to the inner end of said first bore and onrespective centers located at the corners of a polygon substantiallyenclosing the crosssection of said first bore, and a like number ofhardened metal pins of the same basic diameter as said additional borestightly fitted into the latter, those parts of the circumferentialsurfaces of said pins bounding the region therebetween beingappropriately shaped to define between their points of contact a spaceconstituting said orifice.

12. A spinneret according to claim 11, wherein at least one of the sidesof said orifice is inwardly convex.

13. A spinneret according to claim 11, wherein at least one of the sidesof said orifice is inwardly concave.

14. A spinneret according to claim 11, wherein at least one of the sidesof said orifice is flat.

References Cited by the Examiner UNITED STATES PATENTS 1,773,969 8/1930Dreyfus et al. 188 1,902,953 3/1933 Hazell l88 X 2,422,994 6/ 1947Taylor.

3,095,258 6/1963 Scott 18-8 X 3,102,439 9/1963 Martin et al. 761073,174,364 3/1965 Sims 188 X 3,197,812 8/1965 Dietzsch et al. 18-8WILLIAM J. STEPHENSON, Primary Examiner.

1. A SPINNERET PROVIDED WITH AT LEAST ONE CUSPED EXTRUSION ORIFICEHAVING AT LEAST THREE SIDE WALLS WHICH ARE CONVEX INWARDLY OF THEORIFICE, SAID ORIFICE BEING DEFINED BETWEEN A SET OF PINS OF CIRCULARCROSS-SECTION ARRANGED IN A RING FORMATION WITH EACH PIN TANGENT TO TWOOF THE